Q&A: Diagnosis of Skin Lesions

Patients with skin and soft tissue infection may present with cellulitis, abscess, or both. Cellulitis (which includes erysipelas) manifests as an area of skin erythema, oedema, and warmth; it develops as a result of bacterial entry via breaches in the skin barrier. A skin abscess is a collection of pus within the dermis or subcutaneous space. Misdiagnosis of these entities is common, and possible alternative diagnoses should be considered carefully.

This article is for Medical Students & Professionals

This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Infectious Disease articles more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.

In this article:
General principles of management
MCQ exam: clinical scenario
MCQ exam: answer
MCQ exam: explanation

General principles of management

The approach to management of skin and soft tissue infection depends on the clinical presentation:

• Patients with nonpurulent infection (ie, cellulitis or erysipelas in the absence of abscess or purulent drainage) should be managed with empiric antibiotic therapy.
• Patients with drainable abscess should undergo incision and drainage. In addition, antibiotic therapy is warranted if clinical criteria are met.
• Patients with purulent cellulitis (ie, cellulitis associated with purulent drainage in the absence of drainable abscess) should be managed with antibiotic therapy.

MCQ exam: clinical scenario

A 35 year old farmer develops a carbuncle-like painless ulcer on his hands. The ulcer has pustules and a black, necrotic central scab and is surrounded by extensive soft tissue swelling.

This is suggestive of:

a) Syphilis
b) Dermetitis herpetiformis
c) Acne rosacea
d) Anthrax
e) MRSA skin infection

MCQ exam: answer

The correct answer is D.

MCQ exam: explanation

Infection with anthrax is usually seen in people who have come in contact with animal products, especially those who live in the countryside (eg, 'Woolsorter's disease' which is pulmonary anthrax). Typically there is a typical painless lesion (ulcer) at site of infection with a black, necrotic (dying tissue) eschar (scab). Local swelling is prominent.

Reference(s)
1). UpToDate: Cellulitis and skin abscess in adults: Treatment. Available online: https://www.uptodate.com/contents/cellulitis-and-skin-abscess-in-adults-treatment